1. Technical Field of the Invention
The present invention relates to a musical sound waveform synthesizer for synthesizing musical sound waveforms.
2. Description of the Related Art
A musical sound waveform can be divided into different sections by characteristics, including a start waveform, a sustain waveform, and an end waveform. A musical sound waveform produced by playing a performance such as legato, which smoothly joins together two musical sounds, includes a connection waveform where a transition is made between the pitches of the two musical sounds.
In a known musical sound waveform synthesizer, a plurality of types of waveform data parts of musical sound waveforms, including start waveform parts (heads), sustain waveform parts (bodies), end waveform parts (tails), and connection waveform parts (joints) of musical sound waveforms (with each of the connection waveform parts representing a transition part between the pitches of two musical sounds) are stored in a storage, and appropriate waveform data parts are read from the storage based on performance event information, and the read waveform data parts are then joined together, thereby synthesizing a musical sound waveform. In this musical sound waveform synthesizer, an articulation is identified based on performance event information, and a musical sound waveform representing the characteristics of the identified articulation is synthesized along a playback time axis by combining waveform parts corresponding to the articulation, which include a start waveform part (head), a sustain waveform part (body), an end waveform part (tail), and a connection waveform part (joint), representing a pitch transition between the pitches of two musical sounds, so that the waveform parts are arranged along the time axis. Such a method is disclosed in Japanese Unexamined Patent Application Publication No. 2001-92463 (corresponding U.S. Pat. No. 6,284,964) and Japanese Unexamined Patent Application Publication No. 2003-271139 (corresponding US patent application publication No. 2003/0177892).
The fundamentals of musical sound synthesis of a conventional musical sound waveform synthesizer will now be described with reference to FIGS. 11 to 13. Parts (a) of FIGS. 11, 12 and 13 (hereafter referred to as FIGS. 11a, 12a, and 13a, respectively) illustrate music scores written in piano roll notation, and parts (b) of FIGS. 11, 12 and 13 (hereafter likewise referred to as FIGS. 11b, 12b, and 13b, respectively) illustrate musical sound waveforms synthesized when the music scores are played.
When a music score shown in FIG. 11a is played, a note-on event of a musical sound 200 occurs at time “t1” and is then received by the musical sound waveform synthesizer. Accordingly, the synthesizer starts synthesizing a musical sound waveform of the musical sound 200 from its start waveform part (head) at time “t1” as shown in FIG. 11b. Upon completing the synthesis of the head, the musical sound waveform synthesizer still proceeds to synthesize the musical sound waveform while transitioning it from the head to a sustain waveform part (body), since at this time the synthesizer has not received any note-off event, as shown in FIG. 11b. Upon receiving a note-off event at time “t2”, the synthesizer synthesizes the musical sound waveform while transitioning it from the body to an end waveform part (tail). Upon completing the synthesis of the tail, the musical sound waveform synthesizer completes the synthesis of the musical sound waveform of the musical sound 200. In this manner, the synthesizer synthesizes the musical sound waveform of the musical sound 200 by sequentially arranging, as shown in FIG. 11b, the head, the body, and the tail along the time axis, starting from the time “t1” at which it has received the note-on event.
As shown in FIG. 11b, the head is a partial waveform including a one-shot waveform 100 representing an attack and a loop waveform 101 connected to the tail end of the one-shot waveform 100 and corresponds to a rising edge of the musical sound waveform. The body is a partial waveform including a plurality of sequentially connected loop waveforms 102, 103, . . . , and 107 having different tone colors and corresponds to a sustain part of the musical sound waveform of the musical sound. The tail is a partial waveform including a one-shot waveform 109 representing a release and a loop waveform 108 connected to the head end of the one-shot waveform 109 and corresponds to a falling edge of the musical sound waveform. Adjacent loop waveforms are connected through cross-fading so that the musical sound is synthesized while transitioning between partial or loop waveforms.
For example, the loop waveform 101 and the loop waveform 102 are adjusted to be in phase and are then connected through cross-fading, thereby smoothly joining together the two waveform parts (i.e., the head and the body) while transitioning the musical sound waveform from the head to the body. In addition, the loop waveform 102 and the loop waveform 103 are adjusted to be in phase and are then connected through cross-fading while changing the tone color from a tone color of the loop waveform 102 to a tone color of the loop waveform 103 in the body. In this manner, adjacent ones of the plurality of loop waveforms 102 to 107 in the body are connected through cross-fading so that vibrato or a tone color change corresponding to a pitch change with time is given to the musical sound. Further, the loop waveform 107 and the loop waveform 108 are adjusted to be in phase and are then connected through cross-fading, thereby smoothly joining together the two waveform parts (i.e., the body and the tail) while transitioning the musical sound waveform from the body to the tail. Since the body is synthesized by connecting the plurality of loop waveforms 102 to 107 through cross-fading, it is possible to transition from any position of the body to the tail or the like. As the main waveform of each of the head and the tail is a one-shot waveform, it is not possible to transition from each of the head and the tail to the next waveform part, particularly during real-time synthesis of the head and tail.
FIGS. 12a and 12b illustrate how a musical sound waveform is synthesized by connecting two musical sounds when a legato is played using a monophonic instrument such as a wind instrument.
When a music score shown in FIG. 12a is played, a note-on event of a musical sound 210 occurs at time “t1” and is then received by the musical sound waveform synthesizer. Accordingly, the synthesizer starts synthesizing a musical sound waveform of the musical sound 210 from its head, which includes a one-shot waveform 110, at time “t1” as shown in FIG. 12b. Upon completing the synthesis of the head, the synthesizer proceeds to synthesize the musical sound waveform while transitioning it from the head to a body (Body1) since it has not received any note-off event the synthesizer has not received the note-off event, as shown in FIG. 12b. When the synthesizer receives a note-on event of a musical sound 211 at time “t2”, it determines that a legato performance has been played since it still has not received any note-off event of the musical sound 210, and proceeds to synthesize the musical sound waveform while transitioning it from the body (Body1) to a connection waveform part (Joint) that includes a one-shot waveform 116 representing a pitch transition part from the musical sound 210 to the musical sound 211. At time “t3”, the synthesizer receives a note-off event of the musical sound 210. Upon completing the synthesis of the joint, the synthesizer proceeds to synthesize the musical sound waveform while transitioning it from the joint to a body (Body2) since it has not received any note-off event of the musical sound 211. Thereafter, at time “t4”, the synthesizer receives a note-off event of the musical sound 211 and proceeds to synthesize the musical sound waveform while transitioning it from the body (Body2) to a tail. The synthesizer then completes the synthesis of the tail, which includes a one-shot waveform 122, thereby completing the synthesis of the musical sound waveform. In this manner, the musical sound waveform synthesizer synthesizes the musical sound waveform of the musical sounds 200 and 211 by sequentially arranging, as shown in FIG. 12b, the head (Head), the body (Body1), the joint (Joint), the body (Body2), and the tail (Tail) along the time axis, starting from the time “t1” at which it has received the note-on event. The waveforms are connected in the same manner as the example of FIGS. 11a and 11b. 
FIGS. 13a and 13b illustrate how a musical sound waveform is synthesized when a short performance is played.
When a music score shown in FIG. 13a is played, a note-on event of a musical sound 220 occurs at time “t1” and is then received by the synthesizer. Accordingly, the synthesizer starts synthesizing a musical sound waveform of the musical sound 220 from its head, which includes a one-shot waveform 125 of the musical sound 220, at time “t1” as shown in FIG. 13b. At time “t2” before the synthesis of the head is completed, a note-off event of the musical sound 220 occurs and is then received by the musical sound waveform synthesizer. After completing the synthesis of the head, the synthesizer proceeds to synthesize the musical sound waveform while transitioning it from the head to a tail which includes a one-shot waveform 128. Upon completing the synthesis of the tail, the synthesizer completes the synthesis of the musical sound waveform of the musical sound 220. In this manner, when a short performance is played, the synthesizer synthesizes the musical sound waveform of the musical sound 220 by sequentially arranging, as shown in FIG. 13b, the head (Head) and the tail (Tail) along the time axis, starting from the time “t1” at which it has received the note-on event.
Synthesizing the tail is normally started from the time when a note-off event is received. However, in FIG. 13b, the tail is synthesized later than the time when the note-off event of the musical sound 220 is received, and the length of the synthesized musical sound waveform is greater than that of the musical sound 220. This is because the head is a partial waveform including a one-shot waveform 125 and a loop waveform 126 connected to the tail end of the one-shot waveform 125 and it is not possible to transition to the tail during synthesis of the one-shot waveform 125 as described above with reference to FIG. 11 and because the musical sound waveform is not completed until the one-shot waveform 128 of the tail is completed. Thus, even when it is requested that a sound shorter than the total length of the head and the tail be synthesized, it is not possible to synthesize a musical sound waveform to be shorter than the total length thereof. There is also a certain limitation on the shortness of the actual sound of acoustic instruments. For example, musical sound of a wind instrument cannot be shorter than a certain length since the wind instrument sounds for at least the acoustic response duration of its tube even when it is blown for a short time. Thus, for acoustic instruments, it can also be assumed that it is not possible to synthesize a musical sound waveform shorter than the total length of the head and the tail. Also in the case of FIGS. 12a and 12b where the legato is played, it is not possible to transition to the next waveform part during synthesis of the waveform of the joint since the joint includes a one-shot waveform. Therefore, when a legato is played, it is not possible to synthesize a musical sound waveform shorter than the total length of the head, the joint, and the tail.
When a legato with two musical sounds is played for a short time using an acoustic instrument through fast playing, a pitch transition must be started from the note-on time of the second of the two musical sounds. However, the conventional musical sound waveform synthesizer has a problem in that its response to the note-on event of the second musical sound is delayed relative to acoustic instruments. As described above, acoustic instruments have an acoustic response duration, which causes a slow (or unclear) transition between pitches rather than a rapid pitch change when a legato is played using an acoustic instrument. However, the acoustic response duration does not delay the start of the pitch transition. Rather, the response of the conventional musical sound waveform synthesizer to the occurrence of an event is delayed so that it synthesizes a longer musical sound waveform from a short sound played through fast playing, mis-touching, or the like. This causes the musical sound to be delayed and generates a self-sustaining sound from mis-touching. The term “mis-touching” refers to an action of a player having a low skill or the like to generate a performance event that causes unintended sound having a short duration. For example, in a keyboard instrument, the mis-touching occurs when an intended key is pressed simultaneously and inadvertently with its neighboring key. In a wind controller, which is a MIDI controller simulating a wind instrument, the short error sound occurs when keys, which must be pressed at the same time to determine the pitches, are pressed at different times or when key and breath operations do not match.
In this case, a mis-touching sound and a subsequent sound are connected through a joint, so that the mis-touching sound is generated for a longer time than actual mis-action and the generation of the subsequent sound, which is a normal performance sound, is delayed. In this manner, playing a music performance pattern results in a delay in the generation of the musical performance, which causes a significant problem in listening to the musical sound and also makes the presence of the mis-touching sound very noticeable.
As described above, the conventional musical sound waveform synthesizer has a problem in that, when a short sound is played through fast playing or mis-touching, the generation of a subsequent sound is delayed.
As noted above, a short sound may be generated by mis-touching. Even when a performance event of a short sound has occurred through mis-touching, the short sound is synthesized into a long musical sound waveform, thereby causing a problem in that the mis-touching sound is self-sustained.
When a legato with two musical sounds is played for a short time using an acoustic instrument through fast playing, a pitch transition must be normally started from the note-on time of the second of the two musical sounds. However, the response of the conventional musical sound waveform synthesizer to the note-on event of the second musical sound is delayed relative to acoustic instruments. As described above, acoustic instruments have an acoustic response duration, which causes a slow (or unclear) transition between pitches rather than a rapid pitch change when a legato is played using an acoustic instrument. However, the acoustic response duration does not delay starting the pitch transition. On the contrary, the response of the conventional musical sound waveform synthesizer to the occurrence of an event is delayed so that it synthesizes a longer musical sound waveform from a short sound. Even when a performance event of a short sound that overlaps a previous sound has occurred through mis-touching, the short sound is synthesized into a long musical sound waveform, thereby causing a problem in that the mis-touching sound is self-sustained.